The experts surmise Norton is likely a cross between V. aestivalis and an unknown V. vinifera species. There is possibly some contribution of V. labrusca.
Botanists tell us that grapes are members of the genus Vitis, and the well-known European grape varieties are members of the species vinifera. (In case you’ve forgotten, a species is one rung lower in the botanical classification system than a genus.) When the Europeans first came to the New World, they found grapes growing in great profusion